The present invention relates to a sheet supply device to be used for an apparatus for forming images on a sheet, such as an electronic copier, more particularly, a sheet supply device capable of processing one surface and both surfaces of the sheet, and a sheet process method for performing reading and writing with respect to the sheet supplied to a sheet process portion.
In an image forming apparatus, such as the electronic copier as mentioned above, there has been used a document supply device wherein a plurality of sheets (hereinafter referred to as xe2x80x9cdocumentsxe2x80x9d since information is noted thereon) is fed one by one so that they are automatically fed to a position where contents of the document can be read, what is called, an auto document feeder (hereinafter referred to as xe2x80x9cADFxe2x80x9d). Recently, in such a document supply device, a document having information on not only one surface but also both surfaces thereof can be processed.
As a document supply device capable of processing both or two surfaces as well as one surface, for example, there has been disclosed Japanese Patent Publication (KOKAI) No. 7-175279 (prior art 1). In the document supply device disclosed in the above Japanese patent publication, when one surface processing is carried out, documents are stacked on a sheet supply stacker in order from a top thereof, i.e. the top document is the first page, second document is the second page, third document is the third page . . . ; and the documents are fed from the top in this order so that the documents can be supplied to a document reading portion through a supply path in a U-character shape, respectively. Since the documents read at the document reading portion are sequentially ejected as they are to a sheet ejecting stacker through a continuous route in the order of the first page, second page, third page . . . from the bottom, there is no necessity for re-arranging the ejected documents.
Also, the document supply device is provided with a switch-back path in the middle of a sheet ejecting route, and in case two surface processing is carried out, the document, one surface of which has been processed, is again guided to the supply path. However, in case the documents, the two surfaces of which have been processed, are ejected onto the sheet ejecting stacker as they are, the ejected documents have to be re-arranged. Assuming that the first document is G1, the second document is G2, the third document is G3, . . . , when page number assigned to the respective documents thus defined is expressed with a hyphen, i.e. G1-1 is a first page (front surface) of the first document, G1-2 is a second page (back surface) of the first document, G2-3 is a third page (front surface) of the second document, G2-4 is a fourth page (back surface) of the second document, and so on.
As described above, when the documents, the both surfaces of which have been processed, are ejected to the sheet ejecting stacker as they are, the page number of the documents stacked on the sheet ejecting stacker becomes G1-2, G1-1, G2-4, G2-3, . . . in this order from the bottom, so that the documents, the both surfaces of which have been processed, have to be re-arranged to be G1-1, G1-2, G2-3, G2-4 . . . . Thus, in the processing method (document supply method) disclosed in the above Japanese Patent Publication, a process step of (reading of G1-1)xe2x86x92(reverse of G1-1) (reading of G1-2)xe2x86x92(reverse of G1-2)xe2x86x92(skip of G1-1)xe2x86x92(ejection of document G1) is carried out, and the same processing step is repeated regarding the respective second, third, . . . documents. Incidentally, the xe2x80x9cskipxe2x80x9d as mentioned above means that reading of the document is not carried out.
According to the processes, in the two surface process mode, since the document, the both surfaces of which have been processed, is finally reversed, the documents are stacked on the sheet ejecting stacker to be G1-1, G1-2, G2-3, G2-4, . . . in this order from the bottom, so that the documents after completion of the process need not be re-arranged.
Also, in Japanese Patent Publication (KOKAI) No. 7-109060 (prior art 2), there is disclosed a document supply device having a processing method different from the two surface process method as mentioned above. In the document supply device, as in the above prior art 1, documents stacked on a sheet supply stacker are fed in order from a top thereof. However, before a process of the first document is completed, a next document is fed. In other words, when an explanation is given by using the above definition as it is: reading of a surface of document G1 (reading of G1-1)xe2x86x92reverse of the document G1 (reverse of G1-1) and, at the same time, supply of a document G2 and reading of a surface (reading of G2-3)xe2x86x92reading of a back surface of the document G1 (reading of G1-2) and, at the same time, reverse of the document G2 (reverse of G2-3)xe2x86x92supply of a document G3 and reading of a surface (reading of G3-5)xe2x86x92reading of back surface of document G2 (reading of G2-4) and, at the same time, reverse of the document G3 (reverse of G3-5)xe2x86x92supply of a document G4 and reading of a surface (reading of G4-7) . . . , are carried out. That is, when the preceding document, surface of which has been read, is reversed, the next document is supplied to read. According to the document supply method as described above, in the two surface process mode, the process speed can be improved.
According to the prior art 1, in the two surface process mode, there is no necessity for re-arranging the documents ejected on the sheet ejecting stacker, and paths for feeding the documents are simple so that the structure becomes compact. However, after reading of information on a back surface side is completed, the document is again reversed to skip and eject, and thereafter, a next document is supplied. Thus, a process speed in the two surface process mode becomes slow.
Also, according to the prior art 2, although the processing speed in the two surface process mode can be improved, since the documents ejected onto the sheet ejecting stacker are stacked to be G1-2, G1-1, G2-4, G2-3, . . . from the bottom, the ejected documents have to be re-arranged. Further, the order for reading the documents becomes: (G1-1)xe2x86x92(G2-3)xe2x86x92(G1-2)xe2x86x92(G3-5)xe2x86x92(G2-4)xe2x86x92(G4-7) . . . , i.e. instead of continuously reading the front surface and the back surface of one document, another document is entered between the front surface and the back surface of one document to be read, so that after a transfer or print is carried out, pages have to be re-adjusted with respect to the information read in order. As a result, a large capacity of memory is required and control thereof becomes complicated.
In view of the above problems, the present invention has been made, and an object of the invention is to provide a sheet supply device wherein when a two surface processing mode is carried out, a processing speed is shortened and at the same time there is no necessity for re-arranging the processed sheets, and a sheet process method enabling such a process.
Another object of the invention is to provide a sheet supply device wherein when the two surface processing mode is carried out, a large capacity of memory is not required and its control is simple, and a sheet process method enabling such a process.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to attain the above objects, a sheet supply device according to the present invention includes a sheet supply stacker, a supply path for guiding a sheet stacked on the sheet supply stacker to a sheet process portion, a switch-back path positioned at a downstream side than the sheet process portion and guiding the sheet which has passed through the sheet process portion to the supply path by switching back the sheet, and a sheet ejecting stacker on which the sheet having passed through the sheet process portion is ejected to thereby constitute the device such that a front surface and a back surface of the sheet pass through the sheet process portion. After a first supply of a preceding sheet to the sheet process portion is made, the preceding sheet is reversed by the switch-back path to make a second supply to the sheet process portion, and the preceding sheet having been subjected to the second supply is again reversed by the switch-back path to make a third supply to the sheet process portion and then ejected onto the sheet ejecting stacker. A first supply of a next sheet to the sheet process portion is made between the second supply and the third supply of the preceding sheet.
Also, in order to attain the above objects, a sheet process method according to the present invention includes a first supply step for supplying a preceding sheet to a sheet process portion; a second supply step for supplying the preceding sheet subjected to a first supply to the sheet process portion in a reversed state; a first supply step for supplying a next sheet to the sheet process portion after the second supply step; and a third supply step for again supplying the preceding sheet in the reversed state to the sheet process portion after the first supply step of the next sheet.
In the structure as described above, each document to be processed is switched back to be supplied to a sheet process portion three times, and thereafter ejected, so that the pages of the ejected documents need not be re-arranged. Also, the next document is supplied between the second supply and the third supply of the preceding document, so that a process speed can be improved.